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maths help 2

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    A train starts from rest at station A and accelerates uniformly at 3x m s-2 until it reaches a
    speed of 30 m s-1
    . For the next T seconds the train maintains this constant speed. The
    train then retards uniformly at x m s-2 ,until it comes to rest at a station B. The distance
    between the stations is 6 km and the time taken from A to B is 5 minutes.


    Show that 40/x+ T= 300

    i'm sorry i dont know where to start :/

    any help would be very appreciated!
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    (Original post by heatabi11)
    A train starts from rest at station A and accelerates uniformly at 3x m s-2 until it reaches a
    speed of 30 m s-1
    . For the next T seconds the train maintains this constant speed. The
    train then retards uniformly at x m s-2 ,until it comes to rest at a station B. The distance
    between the stations is 6 km and the time taken from A to B is 5 minutes.


    Show that 40/x+ T= 300

    i'm sorry i dont know where to start :/

    any help would be very appreciated!
    Sketch a time-velocity graph of this situation.

    The first interval has time t_1, the second has T, and the third has t_2

    The gradient of the first one is 3x=\frac{30}{t_1} and the gradient of the third one is -x=\frac{-30}{5\cdot 60 -T -t_1}

    Rearrange the first one for t_1 and substitute it into the second one. Rearrange for the wanted form.
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    (Original post by RDKGames)
    Sketch a time-velocity graph of this situation.

    The first interval has time t_1, the second has T, and the third has t_2

    The gradient of the first one is 3x=\frac{30}{t_1} and the gradient of the third one is -x=\frac{-30}{5\cdot 60 -T -t_1}

    Rearrange the first one for t_1 and substitute it into the second one. Rearrange for the wanted form.
    Thank you ! also how could i work out T and x ?
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    (Original post by heatabi11)
    Thank you ! also how could i work out T and x ?
    Well for T you know how much it has traveled, and the distance traveled is the area under your graph. So apply the trapezium area A=\frac{a+b}{2}h and you can find T. Then you can use the part above to find x.

    Keep in mind, you need to turn km into m, and minutes into seconds.
 
 
 
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